APPARATUS AND METHOD FOR EMBEDDING WATERMARK INFORMATION IN COMPRESSED IMAGE DATA, AND APPARATUS AND METHOD FOR RETRIEVING WATERMARK INFORMATION FROM COMPRESSED IMAGE DATA HAVING WATERMARK INFORMATION EMBEDDED THEREIN

摘要

A variable length decoding section extracts a codeword and an additional bit or bits corresponding to the codeword from compressed image data based on a code table. An embedding section embeds watermark information in a prescribed bit of the additional bits extracted by the variable length decoding section. A data connecting section connects the additional bits having the watermark information embedded therein by the embedding section with the codeword extracted by the variable length decoding section to produce a variable length code.